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Publications

Publications by CRAS

2017

In-Programme Personalization for Broadcast: IPP4B

Authors
Foss, JD; Shirley, B; Malheiro, B; Kepplinger, S; Ulisses, A; Armstrong, M;

Publication
Proceedings of the 2017 ACM International Conference on Interactive Experiences for TV and Online Video, Hilversum, The Netherlands, June 14-16, 2017

Abstract
The IPP4B workshop assembles a group of researchers from academia and industry - BBC R&D, Ericsson and MOG Technologies - to discuss the state of the art and together envisage future directions for in-programme personalisation in broadcasting. The workshop comprises one invited keynote, two invited presentations together with a paper and discussion sessions.

2017

Wearable UV Meter - An EPS@ISEP 2017 Project

Authors
Lönnqvist, E; Cullié, M; Bermejo, M; Tootsi, M; Smits, S; Duarte, AJ; Malheiro, B; Ribeiro, C; Ferreira, F; Silva, MF; Ferreira, P; Guedes, P;

Publication
Teaching and Learning in a Digital World - Proceedings of the 20th International Conference on Interactive Collaborative Learning - Volume 1, Budapest, Hungary, 27-29 September 2017

Abstract

2017

Vertical land motion and sea level change in Macaronesia

Authors
Mendes, VB; Barbosa, SM; Romero, I; Madeira, J; da Silveira, AB;

Publication
GEOPHYSICAL JOURNAL INTERNATIONAL

Abstract
This study addresses long-term sea level variability in Macaronesia from a holistic perspective using all available instrumental records in the region, including a dense network of GPS continuous stations, tide gauges and satellite observations. A detailed assessment of vertical movement from GPS time series underlines the influence of the complex volcano-tectonic setting of the Macaronesian islands in local uplift/subsidence. Relative sea level for the region is spatially highly variable, ranging from -1.1 to 5.1 mm yr(-1). Absolute sea level from satellite altimetry exhibits consistent trends in the Macaronesia, with a mean value of 3.0 +/- 0.5 mm yr(-1). Typically, sea level trends from tide gauge records corrected for vertical movement using the estimates from GPS time series are lower than uncorrected estimates. The agreement between satellite altimetry and tide gauge trends corrected for vertical land varies substantially from island to island. Trends derived from the combination of GPS and tide gauge observations differ by less than 1 mm yr(-1) with respect to absolute sea level trends from satellite altimetry for 56 per cent of the stations, despite the heterogeneity in length of both GPS and tide gauge series, and the influence of volcanic-tectonic processes affecting the position of some GPS stations.

2017

Short-term variability of gamma radiation at the ARM Eastern North Atlantic facility (Azores)

Authors
Barbosa, SM; Miranda, P; Azevedo, EB;

Publication
JOURNAL OF ENVIRONMENTAL RADIOACTIVITY

Abstract
This work addresses the short-term variability of gamma radiation measured continuously at the Eastern North Atlantic (ENA) facility located in the Graciosa island (Azores, 39N; 28W), a fixed site of the Atmospheric Radiation Measurement programme (ARM). The temporal variability of gamma radiation is characterized by occasional anomalies over a slowly-varying signal. Sharp peaks lasting typically 2-4 h are coincident with heavy precipitation and result from the scavenging effect of precipitation bringing radon progeny from the upper levels to the ground surface. However the connection between gamma variability and precipitation is not straightforward as a result of the complex interplay of factors such as the precipitation intensity, the PBL height, the cloud's base height and thickness, or the air mass origin and atmospheric concentration of sub-micron aerosols, which influence the scavenging processes and therefore the concentration of radon progeny. Convective precipitation associated with cumuliform clouds forming under conditions of warming of the ground relative to the air does not produce enhancements in gamma radiation, since the drop growing process is dominated by the fast accretion of liquid water, resulting in the reduction of the concentration of radionuclides by dilution. Events of convective precipitation further contribute to a reduction in gamma counts by inhibiting radon release from the soil surface and by attenuating gamma rays from all gamma-emitting elements on the ground. Anomalies occurring in the absence of precipitation are found to be associated with a diurnal cycle of maximum gamma counts before sunrise decreasing to a minimum in the evening, which are observed in conditions of thermal stability and very weak winds enabling the build-up of near surface radon progeny during the night.

2017

Collision avoidance for safe structure inspection with multirotor UAV

Authors
Azevedo, F; Oliveira, AA; Dias, A; Almeida, J; Moreira, M; Santos, T; Ferreira, A; Martins, A; da Silva, EP;

Publication
2017 European Conference on Mobile Robots, ECMR 2017, Paris, France, September 6-8, 2017

Abstract

2017

Monitoring of oxidation phases of copper thin films using long period fiber gratings

Authors
Coelho, L; Agostinho Moreira, JA; Tavares, PB; Santos, JL; Viegas, D; de Almeida, JMMM;

Publication
SENSORS AND ACTUATORS A-PHYSICAL

Abstract
Long period fiber gratings (LPFGs) were used to monitor the characteristics of copper (Cu) thin films when annealed in air atmosphere up to similar to 680 degrees C. The wavelength and the optical power shift of the resonant bands of the LPFGs when coated with the Cu thin films, were measured as a function of the annealing temperature, and were found to exhibit a different evolution comparing to a bare LPFGs. Thin films of Cu deposited on quartz (SiO2) substrates were annealed and analyzed by XRD, SEM/EDS and Raman spectroscopy, allowing to identify the formation of two distinct oxide phases at different temperatures, cuprous (Cu2O-cuprite) and cupric (CuO-tenorite) oxides, respectively. The observed features of the resonant bands of the LPFGs were found to be associated with the Cu oxide phase transitions, indicating the possibility of using LPFGs to monitor, in real time, the oxidation states of Cu thin films by following specific characteristics of the attenuation bands. In addition, LPFGs over coated with the two distinct oxidation phases of Cu were characterized for refractive index sensing in the range between 1.300 to 1.600, leading to the conclusion that the sensitivity to the refractive index of the surrounding medium of Cu coated LPFGs sensing systems can be temperature tuned.

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